> I am working on an update to the SPIN RDF syntax to support the latest
> SPARQL 1.1 UPDATE draft. The latter contains a comprehensive
> description of DELETE/INSERT [1], followed by an equally comprehensive
> coverage of DELETE [2] and INSERT [3]. The latter two appear very much
> redundant, and are IMHO even confusing. DELETE and INSERT appear to
> be a true subsets of DELETE/INSERT, and even the Grammar [4] does not
> distinguish them.

These operations are indeed degenerate cases of DELETE/INSERT. They were initially proposed as separate cases, to avoid a case in the grammar where both DELETE and INSERT are omitted, but they have now evolved to be subsets of the more general DELETE/INSERT operation. They have been left in the documentation as informative clarifications of very common operations. In this respect, they are directed more to users than to implementors of the specification, and we see some value in keeping them.

> Could those two simply be dropped, to simplify the documents and
> reduce the (apparent) implementation burden?

Rather than removing these sections, they have been explicitly marked as "Informative" with an explanation that a correct implementation of DELETE/INSERT will correctly cover these operations.